These videos were taken with an oscilloscope, real time and have not been manipulated.
We used for the test an NEUTRAL X-PRO switching between BYPASS / ON STEREO DREI
Modulation & Overdrive
You can see the square waves are modified without affecting the sine.
Triangle & Square waves
You can watch as triangular and square waves are reinterpreted to be more like sine waves and avoid problems with sound reproduction.
All videos together.